**What is bulk density and % of voids of fine aggregates**

● **introduction** :- in this article discuss about what is bulk density and % of voids of fine aggregates and their nature. As we know bulk density is also called as apparent density or volumetric density which is a not intrinsic property of any material and it can be changed depending on how the material is handled.

Bulk density is defined as ratio of mass of fine aggregates by the total volume they occupy. Total volume means volume of fine aggregate, volume of inter particles between them and volume of internal pores present in fine particles. In this article discuss about finding the bulk density and voids of fine aggregate and their Test procedure and also know about what is loose bulk density what is Rooded bulk density ,what is loose fine aggregate what is compacted fine aggregate.

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**What is bulk density and their types**

Bulk density is also known as Apparent density or volumetric density and it is property of powder and fine granules and other divided material like minerals, chemical substance, ingredients and food stuffs. It is defined as mass of fine particles of aggregate divided by the total volume they occupy.

**Total volume of fine aggregate is consist of sum of volume of particles ,volume of inter- particles and volume of internal pores between particles**.

Bulk density is not an intrinsic property of any material and it can change depending on how the material should be handled. For example if we poured fine aggregate into cylindrical metal measurement unit will have loose bulk density and when it is disturbed with Tamping rod the fine aggregate will go and settle closer together resulting in higher bulk density.

**Types of bulk density of fine aggregate**

Bulk density of fine aggregate is categorised into two categories depending on how they can poured and settle into cylindrical metal measurement unit

**1) Loose bulk density**

**2) Rooded bulk density**

1) **Loose bulk density** :- it is the ratio of mass of loosely packed fine aggregate without Tamping or rooded to the total volume they occupy.

2) **Rooded bulk density** :- it is the ratio of mass of compacted packed of fine aggregate with the help of Tamping or rooded to the total volume they occupy.

**Types of fine aggregate according to packing**

There are two types of fine aggregate according to mass and packing

1) **Loosely fine aggregate**

**2) Compacted fine aggregate**

1) **Loosely fine aggregate** :- mass of fine aggregates which are poured into cylindrical measurement unit without any disturbing or setteling with Tamping rod

2) **Compacted fine aggregate** :- mass of fine aggregates which are poured into cylindrical measurement unit after disturbing or setteling with Tamping rod.

**What is the importance of finding bulk density of fine aggregate and percentage of voids**

Bulk density of fine aggregate and their specific gravity along with bulk density of cement fine aggregate and coarse aggregate and specific gravity of coarse aggregate and cement is quite helpful in finding in design of mix concrete like M20,M25,M30 and so on- .

When we make design of building structure column beam slab it has requirement of casting of RCC. casting of RCC work mix concrete should be prepared at the construction site according to design of concrete mix which type of material should be provided, and prepared concrete mix should be tested at the construction site.

**Voids** :- the space between the fine particles of aggregate which was not occupied by solid material that is known as voids.

**Test procedure for finding loose bulk density of fine aggregate**

**Test procedure for finding loose bulk density procedure are following**

1) **Apparatus required for the test**

a) weighing balance

b) Tamping rod

c) straight edge

d) Sand sample

e) cylindrical metal measurement of 3 Litre capacity

f) observation sheet

**Tamping rod** :- tamping rod is 16mm rounded bar of length 600 mm which have tamping nose at one end and second end is rounded.

2) first we take clean empty cylindrical measurement unit capacity of 3 litre and weighted it on the weighing balance.take and note their weight in observation sheet.

**W1 = weight of empty cylindrical metal measurement unit = 2.685 kg**

3) than we poured loosely packed fine aggregate into empty metal measurement having capacity of 3 Litres with the help of scoop and sand will be poured into vessel least height of 5 centimetre to the top,now vessel fulfilled with sand, and care is being taken that extra amount of sand is removed by using straight edge and levelling the top surface of vessel filled with sand without disturbing it to setteling.

Now weighted the cylindrical metal measurement which was filled with sand with the help of weighing balance and take their reading

**W2= weight of cylindrical metal measurement filled with loosely fine aggregate = 6.88 kg**

4) now calculating the net loose weight of sand by subtracting weight of empty cynical metal measurement from the the weight of cylindrical metal measurement filled with loosely fine aggregate

Net loose wt = 6.88 _ 2.685 kg

Net loose weight = 4.195 kg

Volume of sand = 3 Litre

Loose bulk density = Net loose wt/Volume

Loose bulk density = 4.195 kg/3 L

**Loose bulk density = 1.398 Kg/L**

**Test procedure for finding Rooded bulk density of fine aggregate**

1) first we take clean empty cylindrical measurement unit capacity of 3 litre and weighted it on the weighing balance.take and note their weight in observation sheet.

**W1 = weight of empty cylindrical metal measurement unit = 2.685 kg**

2) than we poured loosely packed fine aggregate into empty metal measurement having capacity of 3 Litres with the help of scoop in three layer first we filled 1/3rd part of vessel and 25 stroke is applying evenly distributed with the help of tamping rod and after that 2/3rd part is filled with pouring sand and again we apply 25 strokes with tamping rod and last layres will be poured into vessel least height of 5 centimetre to the top,

now vessel fulfilled with sand and again applying 25 strokes with tamping rod their top surface is levelling equal to height of cylindrical metal measurement with the help of straight edge.

Now take the weight of cylindrical metal measurement filled with compacted fine aggregate with the help of weighing balance and take their reading

**W2= weight of cylindrical metal measurement filled with compacted fine aggregate = 7.435 kg**

3) now calculating the net compacted weight of sand by subtracting weight of empty cynical metal measurement from the the weight of cylindrical metal measurement filled with compacted fine aggregate

Net compacted wt = 7.435 _ 2.685 kg

Net compacted weight = 4.75 kg

Volume of sand = 3 Litre

Rooded bulk density = Net compacted wt/Volume

Rooded bulk density = 4.75 kg/3 L

**Rooded bulk density = 1.583 Kg/L**

**How to calculate % of voids in fine aggregates**

**Voids** :- the space between the fine particles of aggregate which was not occupied by solid material that is known as voids. And percentage of voids present in fine aggregate is calculated with the help of specific gravity of fine aggregate and their Loose bulk density by the following formula

**% of voids = {(Gs _R)/Gs}×100**

Where Gs = specific gravity of fine aggregate and their value is 2.62

R = loose bulk density of fine aggregate = 1.398 kg/L

Putting all this values in formula we get

% of voids = {(2.62 _ 1.398)/2.62}×100

% of voids = (1.222 /2.62)×100

% of voids = 0.466×100

Hence % of voids of fine aggregate = 46.6%